VI 
PREFACE 
her indebtedness to Dr. H. D. Waggoner, head of the Biology De¬ 
partment of this school, for his large contribution to the subject 
matter of this book, his unfailing advice, and his criticism of 
its contents and of the actual use of the exercises preceding their 
compilation in their present form. 
Mary A. Bennett 
Macomb, Illinois 
June, 1926 
